Ammonia oxidizing method



1930; l. HECHENBLElKNER ET AL 1,743,646

AMMUNIA QXIDIZING METHOD Filed May 1927 2 Sheets-6119s: 1

INVENTORS I. HECHENBLEIKNER and BYN,T|TLE5TAD ATTORNEYS Feb. 25, 1930.I. HECHEINBLEIKNER ETAL 1,748,646

madam oxmzmd METHOD Filed May' 18, 1927 2 Sheets-Sheet 2 FILTER 40 l mI[/46 I I 5 NITRIC OXIDES 1| I o I TOABSORPTION I 8 1 v E FEED OF 505Z53 AMMomA LIQUOR :1 i 1 I I45 7 Z93 z 2 g 3 P4 .I53

E D. E E

i I :5 l 1 27a I I .5! CONVERTER I I ans Zea E1 :1 z I w T 255 J A EREXIT INVENTORS 1. HECHENBLEIKNER and ATTORNEYS Patented Feb. 25, 1930UNITED STATES .INGENUIN HECHENBLEIKNER AND NICOLAY TITLESTAD, OFCHARLOTTE, NORTH PATENT OFFICE I CAROLINA, ASSI GNORS T0 CHEMICALCONSTRUCTION COMPANY, OF'CHARLOTTE,

NORTH CAROLINA, A CORPORATION OF. NORTH CAROLINA AMMONIA oxrmzine METHODApplication filed May 18,

This invention relates to the process and apparatus for the oxidation ofammonia. The apparatus for carrying out this process is described andclaimed in our divisional appli2cation, Serial No. 352,095, filed April3, 19 9. a

As commonly practiced this process utilizes ammoniacal liquor as the rawmaterial. In essence the process consists in mixing ammonia in itsgaseousform with air or oxygen, as the case may be, and passing the mixture through a catalytic. converter, where after the process is oncestarted the ammonia interacts with the oxygen or with the oxygen in theair and is converted into oxides of nitrogen. This reaction isexothermic, generating a large amount of heat which is commonly utilizedfor preheating the mixture of the gaseous ammonia with the air or theoxygen before it reaches the converter.

In the process as commonly practiced however, the raw material utilizedis usually an ammoniacal liquor. Before the conversion can take placethe ammonia is separated from the liquor by allowing the liquor totrickle downwardly through a stripping tower which is filled with smallbodies of solid inert material serving to divide the liquor into aplurality of small streams. The air is blown into the stripping tower atthe bottom thereof'and traveling upwardly meets the streams of liquorand serves to drive off a substantial proportion of the ammoniadissolved in the liquor. In order, however, to

attain a fairly complete separation of the ammonia from the liquor ithas been found necessary to heat the bottom of the stripping tower byvarious means thereby in part preheating the air that enters the towerand in part directly heating the ammoniacal liquor at, the bottom of thetower and assist in the separation of the gaseus ammonia from theliquor. Steam has been used for this pur pose in sufiicient quantitiesfor the evaporation of the ammonia and for heating up the water and forcompensating for heat losses.

It is very important that the steam or heat supply used in this processbe regulated properly for'the reason that any excessive amount oflieatwill evaporate the large stock of am- 1927. Serial No. 192,462.

. monia which is present in the stripping col- Repeated efforts havebeenfmade to overcome these difliculties by the installations ofautomatically controlled steam valves and the like. This involvesexpensive and complicated installations which do not always workreliably and which are always much too expensive and impractical forsmall installations.

It is the object of the present invention to overcome the abovedifficulties in a very simple and inexpensive manner.

. One of the objects of the present invention is to obviate thenecessity of using any external source of heat for the vaporization ofthe ammoniacal liquor'or for the separation of the gaseous ammonia fromits mother liquor. In the present invention the heat of the exothermalreaction which takes place in the converter is utilized as a source ofheat for separation of the gaseous ammonia from the liquor.

Another object of the present invention is to make'the two steps of theprocess above described, namely, the step of the separation of thegaseous ammonia from the mother liquor and the exothermal reaction,depend one 'upon the other in such a manner that the zation of theammoniacal liquor is obviated I the oxidation of ammonia, the sameprocess and apparatus may be applied to other processes in which anexothermal reaction takes place and is preceded by the vaporization ofthe raw material. 1

The process and apparatus will be understood more clearly from thedrawings and the description thereof which follows.

In the drawings, Fig. 1 illustrates one embodiment of the presentinvention,

Fig. 2 is a cross section on the lines 22 of Fig. 1, and 1 Fig. 3 showsanother embodiment of the present invention.

In the drawings 10 indicates a storage tank of ammoniacal liquor, llis alevel tank having a pipe 12 connecting the top thereof with the top ofthe storage tank 10. The pipe 12 serves to maintain a predeterminedlevel of ammoniacal liquor in the level tank 11. A pump 13 serves tofeed the liquor from the storage tank 10 into thetop of the level tank11. Aconduit 14 leadsfrom a point near the bottom of the level tank 11to a point approxi- ;mately near the middle of the stripping tower orvaporizing column 15. The conduit 14 is provided with an extension 16which projects into the vaporizing tower 15 and is additionally providedwith a valve 17 which may be adjusted to any desired rate-of flowofammoniacal liquor into the vaporizing column 15. i

It should be noted at this point that the rate offoperation of theprocess disclosed herein is controlled entirely and solely by theadjustment of'the valve .117. In prior processes the same valve 17served as a controllingelement of the rate of operation of. the system,but the system in addition th ereto was subjectedto possible variationsdependent upon-thevariations in the source of external heat employed forheating the vaporizing column. By the present invention and by theprocess which constitutes anembodiment of the present invention and.disclosed herein this external source of varia-' bility is eliminatedand the only adjustment necessary is the adjustment of the valve 17.With the valve 17 onceproperly adjusted the various steps of the processand the various parts of the apparatus serve as a check one upon theother, with the result that the process may then continue at a'uniformrate.

The vaporizing tower 15 is provided with a foraminous false bottom 17which permits the passage of air therethrough upwardly and the passageof waste liquor therethrough downwardly. The space above the falsebottom 17 is filledwith small bodies of inert solids 18 to a. pointwhich falls somewhat short of the top'of the tower. The vaporizing tower15 is provided with a chamber 19 immediately below the foraminous bottom17 for the reception of the waste liquor 20 which is maintained at aconstant level by the waste overflow 21. An air blower 22 blows air intothe-chamber 19 which passes upwardly in the column 15 and serves to aidin the,vaporization of the mother liquor that trickles down in smallstreams on and between the solids 18. The tower 15 rests over the watertank- 23 whose function andxgrelation to the other parts of theapparatus andthe rocess' will be more fully described hereina ter.

The mixture of air and gaseous a mmonia passesout of the vaporizingtower anddownplatinum gauze or any other suitable catalyst. I

This reaction is accompanied by the generation of heat so thattheresultant productsv and thereby transferring some of its heat to.

the gaseous mixture flowing therein. The reaction products then pass outof the system through the conduit 30 and are directed to a for theabsorption of the oxides I Glover tower of nitrogen. a

Except for the water tank 23, the process and apparatus so vfardescribed are 'old andwell known in the art. The present invention isdirected to a modification of the process 3 the converter. For thispurpose, the conduit 3 28 carrying the heated reaction products issurrounded by. a water jacket 31 which in turn is put into communicationwith thwater tank 23 by means of the pipes 32 and 33, the

pipe 32 connecting the. upper portions of the 3 tank-23and the jacket31, whereas the pipe 33 connects the. lower portions of the. pipe 33 andthe jacket 31.

. The reaction products passing through the conduit 28 transfer theirheatto the water in lates in accordance with the principle of thethermal siphon in the closed system formed by the tank 23, the jacket 31and the connecting pipes 32 and 33.

The water jacket 31 serves as a heater for the water tank 23 'and willhereinafter be referred to as the water heater. This heater is given aheating surface which is just sufficient to supply the heat required forthe separation of the gaseous ammonia from the ammoniacal liquor andalso supply the necessary concomitant heat losses. The specificdimensions and design of the heater will depend uponthe size of theinstallation and it may be stated that in all cases the heater willreduce the temperature of the reaction products coming from theconverter approximately 150 to 200 C.

Assuming a constant flow of ammoniacal liquor into the vaporizing tower15 and a constant flow of air in the system, the rate of vaporization ofthe ammoniacal liquor, or rather, the rate of separation of gaseousammonia from-the ammoniacal liquor will depend upon the temperature ofthe water tank 23, which in turn depends upon the temperature of theheater 31. On the other hand, the temperature of the reaction productsflowing through the conduit 28 which determine the temperature of theheater 31 itself depends upon the concentration of gaseous ammonia inthe mixture that'passes into the converter 26. In this system,therefore,'the process will continue uniformly and will depend entirelyupon the rate of flow of ammoniacal liquors in the vaporizing tower 15.Should it be 'desired at any time to increase the rate of operation ofthe process, all that is necessary is to adjust the valve 17 to thedesired increased flow of ammoniacal liquors into the system. This willbring about a richer gaseous mixture entering the converter 26, causingthe generation of a larger amount of heat and an increased temperatureof the reaction products. This will cause the generation of a largeramount of heat, a rise to some extent in temperature, because of heatlosses being relatively less, and higher gas velocity through heater 31.This increase, however, of the amount of heat available for theseparation of the gaseous ammonia from the mother 5 liquor will not beso large as to cause the 7 of any kind.

sudden or rapid vaporization of the large store of ammonia withinthevaporizing tower. In other words, the process disclosed herein isinherently and automatically self regulating without the application ofany external source of heat or any external device This process isofgreat advantage when applied to the ammonia oxidation processes.

The basic principle involved herein, however, may also be applied to anyone of a number Fig. 3 shows a modification of the process and apparatusdisclosed in Fig. 1. For the -purpose of comparison and for the purposeof makin this fi re readil If i i 'ble reference niimerals w hich arereference numerals shown in Fig. 1 by t e ddition of the digit 3 theretowill be use for indicating similar parts. I

In Fig. 3, 153 indicates the stripping or vaporizing column whichreceives its ammoniacal liquor through the conduit 143. The mixture ofgaseous ammonia and air passes through the conduit 243 and'through thefilter 40, and .then through the conduit 253 shown in dotted lines whichis surrounded by the preheater 293, and then along the conduit 273 intothe converter 263. The reaction products pass through the conduit 283transferring some of their heat to the water heater 313 and then throughthe preheater 293 and out through theconduit 303 to the absorption towernot shown. As in the apparatus and process shown in Fig. 1, the heater313 communicates with the water tank 233 by means of the pipes 323 and333. In this modification of the invention, however, the tank 233 isopen at the top and serves to receive the heated in the chamber 44 andpasses through conduit '45 into the bottom of the stripping orvaporizing column 153 at the point immediately over the level of the hotWater and waste liquor in the tank 233. The stripping or vaporizingtower 153 is additionally provided with -a cooler 46 which may be soconstructed as to surround the tower at the top thereof or in similarinstallations it may be enclosed inside. the tower. The cooler 46 servesto condense any water vapor that may pass up the column and thusprevents the entry of any water vapor into the converter 263. I

The principle of operation .of the process and apparatus shown in Fig. 3is the same as that shown in Fig. 1. The heat necessary for theseparation of the gaseous ammonia from the ammonia liquor is derivedentirely from the heat reaction products with the same advantageousresults as those described before. The rate of the reaction will dependentirely upon the rate of feeding of the ammonia liquor. The heater 313is so designed as to supply the necessary amount of heat for thatpurpose and also to supply the heat losses of thesystem. The process,like the process described in connection with Fig. 1 is inherentlyautomatically regulated to maintain a uniform rate of reaction withinthe converter and thus obviating the possibilities of burning out theplatinum gauze. In addition to these advantages in the process andapparatus shown in Fig. 3, the. air entering the vaporizing column ispreheated and the cooler or condenser 46 serves to prevent the increaseof water vapor into the converter.

The process and apparatus shown in Fig. 3, like that shown in Fig. 1,may, if desired, be applied to processes other than the oxidation 0ammonia in which an exothermal reaction takes place which is preceded bythe vaporization of the raw material.

It should also be noted that in the process shown in Fig. 3 the heatexchanger 293 works on the counter-current principle which makes itpossible to utilize almost all of the heat generated in the converter263, part of the heat being transferred to the vaporizing towerandutilized for the separation of the ammoniacal gas from the motherliquor, and the remainder of the heat being utilized for preheating thegaseous mixture before it enters the converter 263.

This system as shown in either Figs. 1 or 3, isvery flexible and willnot require any at tention. There. are no. complicated valves o'rmechanism to watch, whichis of special advantage in small plants. Therecan be no fear of excessive heat in the system, as the quantity islimited by the heat of reaction at the capacity of the plant and theheat ing surface of the heater. There can be no sudden changes in heatbecause of the limited quantity of heat at disposal.

In case of operation of the plant at lower than rated capacity, therewill theoretically be an excess of heat, because the heating surface ofthe heater is then comparatively larger. The heat losses of the plantwill, however, fully or partly take care of this. The temperature of gasentering the heater will be less, the flow slower, which reduces I.

the heat transmission approximately by the square root of the velocity,and the heat loss of the stripping column relatively higher. Alltakeninto consideration there will, by correct design, .be approximatelyconstant conditions at all rates of flow. The small fluctuations andirregularities that may occur will be taken care of by the cooler at thetop of the stripping column.

It will also be apparent that while we have shown and described ourinvention in the preferred form,m'any changes and modifications may'bemade in the structure disclosed without departing from the spirit of theinvention, .definedin the following claims. 7 I

We claim 1. In the process for the oxidation of ammonia; comprisingseparating ammonia from to an exothermic reaction, the step oftransferring reaction heat to the ammonia liquor for the separation ofthe ammonia therefrom.

2. In the process for the oxidation of ammonia comprising separatingammonia from ammonia liquor and subjecting the ammonia to an exothermicreaction, the steps of transfer-ring reaction heat to a fluid andtransferring heat from the fluid to the ammonia liquor for theseparation of the ammonia therefrom.

Y 3. In the process for the oxidation of ammonia comprising separatingammonia from ammonia liquor and subjecting the ammonia to an exothermicreaction, the steps of transferring reaction heat to a circulating fluidand transferring heat from the fluid tothe ammonia liquor.

4. In the process for the oxidation of ammonia comprising separatingammonia from ammonia liquor, mixing an oxidizing medium with saidammonia and subjecting said mixture to an exothermic reaction, the stepof transferring reaction heat to the liquor and to the oxidizing medium.

5. In the process for the oxidation of ammonia comprising separatingammonia from ammonia liquor, mixing air with said ammonia and subjectingsaid mixture to an exothermic reaction, the steps of transferringreaction heat to a circulating fluid and trans- 7. 'In the process forthe oxidation of am-' monia comprising separating ammonia from ammonialiquor, mixing air therewith andsubjecting the mixture to an exothermicre action, the step of automatically regulating the speed of the processby transferring reaction heat to the -ammonia liquor and the air.

8. In theprocess for the oxidation of am- -monia comprising separatingammonia from 'ferring heat from the-fluid to the ammonia ammonia liquor,mixing air therewith and subjecting the mixture to an exothermicreaction, the step of automatically regulating the speed of the processby transferring reaction heat to a body of water and transferring theheat from the body of water to the ammonia liquor and to the air.

9. In a process comprising subjecting a material to vaporization andsubjecting the product of vaporization to an exothermic reaction, thestep of transferring reaction heat to the material for its vaporization.

10. In a process comprising subjecting a material to. vaporization andsubjecting the product of vaporization to an exothermic reaction, thesteps of transferring reaction heat to a fluid and transferring heatfromthe fluid to the material for its vaporization.

11. In a process comprising separating a gas from a liquor containingsaid gas and sub jecting said gas to an the reaction heat to the stepsof transferring liquor to separate the gas from the liquor.

12. In a process comprising separating a gas from a hquor containmg saidgas, mg a reactive fluid with said first gas, and

suhjectmg said mixture toan exothermic reaction, the step oftransferring react-ion heat to the liquor andto the reactive gas.

13. In a process comprising separating a gas from a liquor'containingsaid gas, mixing air with said gas, passing the mixture into a reactionchamber and subjecting the mixture to a catalytic exothermic reaction,thev steps of transferring reaction heat to the liquor and the air. V

Signed at Charlotte in the. county of Mecklenburg and State of NorthCarolina,

this 16 day of Map IA. D. 1927.

INGENUIN ECHENBLEIKNER. NICOLAY TIT LESTAD.

exothermic reaction, the

